Predation by Crested Caracaras (Caracara plancus) on Nests of the Endemic White-Headed Steamer-Ducks (Tachyeres leucocephalus)

FORMOSO, ANAHÍ E.; D'AGOSTINO, ROMINA L.; AGÜERO, M. LAURA

JOURNAL OF RAPTOR RESEARCH

RAPTOR RESEARCH FOUNDATION INC

Año: 2024 vol. 58

0892-1016

ABSTRACT.—Crested Caracaras (Caracara plancus) are diurnal, opportunistic raptors that feed on a greatvariety of prey, including carrion, nestlings, and eggs. In the coastal area of Chubut province, Argentina, theyco-occur with White-headed Steamer-Ducks (Tachyeres leucocephalus), an endemic and vulnerable species.Here we report observations of Crested Caracaras on nests of White-headed Steamer-Ducks in theInterjurisdictional Marine Park in Northern San Jorge Gulf, Chubut, Argentina. We looked for steamerducknests on islands and islets in the park from September to December in 2015 and 2016. We installed cameratraps at 21 nests and operated them for a total of 166 camera-nights. We detected Crested Caracaras 27 times,at 15% and 37% of the duck nests in 2015 and 2016, respectively. We corroborated predation on eggs aftervisiting nests, although we were not able to see Caracaras directly eating eggs on pictures. The timing ofCrested Caracara visits to duck nests corresponded with the recess pattern (i.e., periods of time when nest isunattended during incubation) of the White-headed Steamer-Ducks. Crested Caracaras are generally visualpredators and they likely observe the steamerducks and take advantage of their incubation patterns. Ourcamera data contribute to improving our understanding of Crested Caracara ecology and potential limitingfactors on White-headed Steamer-Duck nesting success.